1. Field of the Invention
The present invention relates to a shredder and a shredding method that shred a recording medium to which a holographic memory has been added.
2. Description of the Related Art
A holographic memory that records information in the form of a hologram is a three-dimensional optical memory with which recording (including temporary storage) of a large capacity is possible. A holographic memory is also a page-type memory that has high-speediness resulting from lump recording/playback of two-dimensional data per page unit. For this reason, holographic memories are gaining attention as next-generation recording media.
As one example of an application of a holographic memory to an image recording medium (recorded medium), a holographic memory with which high-density recording is possible is disposed on the surface of an image recording medium, and information is recorded in this holographic memory. Thus, it becomes possible for the image recording medium to provide the large amount of information recorded in the holographic memory in addition to image information viewed from the surface of the image recording medium.
For example, an OHP sheet that includes a transparent plastic film and a receiving layer, which comprises a light-transmitting resin that receives toner, has been proposed. A transparent hologram that manifests a reproduced image or changes in the amount of transmitted light, where diffracted light has been attenuated, is disposed on the surface of the OHP sheet for verifying the authenticity of the OHP sheet (e.g., see Japanese Patent Application Laid-Open Publication No. 9-90665).
In a Fourier transform hologram where an image is Fourier-transformed with a lens and recorded, image information is dispersed and recorded on a recording surface in correspondence to the spatial frequency thereof. With such a Fourier transform hologram, the entire image can be read even with a portion thereof. For this reason, even if such an image recording medium is shredded with a shredder, the holographic memory portion is only shredded to a piece of about several millimeters, and the holographic information dispersed and recorded in that portion is not shredded. Thus, the data recorded in the holographic memory is readable and there is the potential for the information that had been recorded, such as confidential information, to leak to the outside.
Although holographic memories are extremely useful recording media that are thin and can be written/read even if they are folded or cut small to a piece of about several millimeters, the problem of security at the discarding stage remains. Namely, as long as a portion of the memory is readable, there is the potential for the content of the information that had been recorded in the entire memory to be read.